Roofing Underlayment

ABSTRACT

The present invention provides a composite sheet material ( 10 ) that is particularly useful as an underlayment material in roofing applications. In particular, the present invention provides a composite sheet material ( 10 ) that is flexible, relatively lightweight, resistant to water as well as being water vapor permeable and resistant to tearing. In addition, the composite sheet material ( 10 ) includes an outer non-skid surface ( 18 ) that can help prevent slippage of workers during installation of the roofing system. Embodiments of the composite sheet material can help provide a roofing\structure, such as a shingled roof, with fire resistance so that the roof can meet the Fire Resistance requirements of ASTM E  108 - 07 a, Class A.

FIELD OF THE INVENTION

The present invention relates to composite sheet materials for use as an underlayment material in roofing applications.

BACKGROUND OF THE INVENTION

Roofing underlayment materials are used in a wide variety of roofing applications. Roofing underlayment was originally used as a temporary protection against the elements during construction, but is now an integral part of a home's overall roof system. Roofing underlayment is typically used under asphaltic shingles, shakes, tile, cedar, metal, and various other roofing panels to provide a second layer of protection on top of the sheathing to help keep moisture out of the interior of the building. Roofing underlayment materials can also be used to provide fire resistance, wind uplift resistance, puncture resistance, and resistance to wind-driven rain. In addition to providing the above properties, it may also be desirable for the roof underlayment material to be breathable to allow for trapped moisture vapor to pass through from the interior of the building.

One of the earliest and most widely used types of roofing underlayment materials is asphalt-saturated felt, also commonly known as builder's felt or felt paper. Asphalt-saturated felt has been used as a roofing underlayment material for more than 50 years. The felt is made from a paper base that is impregnated or saturated with asphalt to make it more resistant to the elements. Some papers are actually coated in asphalt, while others are truly saturated. Felt paper is generally installed by being rolled across a roof deck and is then stapled or nailed in place. Shingles are then installed over the top of the previously installed felt paper. Although inexpensive and fairly easy to install, felt paper can be susceptible to tearing, especially in hot temperatures, and makes for a slippery surface to walk on while installing the roof covering. Asphalt felt also tends have poor breathability which can result in moisture vapor being trapped within the roofing system.

Recently, synthetic roofing underlayment materials have been introduced into the market and are gaining acceptance in the roofing industry. Synthetic roofing underlayments are based on polymeric materials, such as polyethylene and polypropylene. Synthetic roofing underlayments are generally more durable than asphalt-saturated felt, waterproof, and breathable.

Although having many advantages over felt paper, many synthetic roofing underlayment materials still have some disadvantages.

In US patent application US2010/0056004A1 non-skid properties of a roof underlayment are provided via the coefficient of friction of a coating. The application discloses a skid-resistant roof underlayment comprising a spunbond nonwoven web and a coating on at least one surface having a coefficient of friction of at least 0.40.

Thus, there still exists a need for roof underlayment materials that are easy to install and have non skid properties and help fire resistance to the roof system.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a method of installing a roof system comprising covering an exterior surface of a roof structure with composite sheet material, the composite sheet material comprising a substrate forming at least a part of a first surface at the exterior of the composite sheet material and a film layer forming at least a part of a second surface at the exterior of the composite sheet material opposite to the first surface. The film layer is arranged to control the breathability of the composite sheet material. The method further comprises positioning the composite sheet material onto the roof structure so that the second surface faces towards the roof structure and the first surface provides a non-skid surface.

By the application of this method, there is a reduced risk of slipping while the sheet material provides a non-skid surface. At the same time, in a simple embodiment the material used is a composite of only two layers (the substrate and the film). As the film faces the roof structure, it is not necessary to impart non-skid properties to the film, which can thereby be optimized for the breathability without being effected by measures to give it non-skid properties. As only two layers are needed to provide non-skip properties and the breathability, the composite sheet material has a relatively lighter weight than other underlayment material (e.g. having multiple fabric and/or film layers). As a consequence the method is relatively easy and more roof can be covered per roll and for instance less rolls need to be carried to the roof. In embodiments the film layer is also used to optimize for instance the water barrier properties and/or to influence the flame retardant properties of roofs in which the composite sheet material is used.

According to an aspect of the invention a composite sheet material for use as a roof underlayment is provided, wherein the composite sheet material comprises a substrate forming at least an exposed part of a first surface at the exterior of the composite sheet material and a film layer forming at least a part of a second surface at the exterior of the composite sheet material opposite to the first surface wherein the exposed part of the first surface provides a non-skid surface. Furthermore the wherein the film layer has a basis weight of at least 50 g/m², 70 g/m² or 75 g/m².

The invention therefore provides a composite sheet material that needs only two layers wherein the substrate provides non-skid properties. The film is optimized for breathability without being effected by measures to give it non-skid properties. As only two layers are needed to provide non-skip properties and the breathability, the composite sheet material has a relatively lighter weight than other underlayment material (e.g. having multiple fabric and/or film layers). As a consequence more roof can be covered per roll of equal weight as roll of roof underlayment with higher basic weights and for instance less rolls need to be carried to the roof. In embodiments the film layer is also used to optimize for instance the water barrier properties. The high basis weight of the film gives the composite sheet material flame retardant properties when used in a roof.

Advantageously, embodiments of the composite sheet material provided excellent barrier, strength and anti skid properties without the need for additional layers, such as additional reinforcing mesh or scrim layers, multiple film barrier layers, or additional coating or gritty materials for improving the non-skid properties of the outer substrate layer.

The invention also provides a construction material comprising a composite sheet material and a roof deck, wherein the composite sheet material is attached to the roof deck with the second surface facing the roof deck. The invention also provides a roof comprising such a construction material an a multiplicity of courses of roofing shingles attached to the construction material. Furthermore a structure is provided by the invention, the structure comprising such a roof.

The roof deck according to this invention uses the advantages of the composite sheet material as described above. Note that the roof deck can be pre-fabricated.

Furthermore the invention provides for a use of a composite sheet material as a roof underlayment, the composite sheet material comprising a substrate forming at least a part of a first surface at the exterior of the composite sheet material and a film layer forming at least a part of a second surface at the exterior of the composite sheet material opposite to the first surface wherein the first surface provides a non-skid surface.

This aspect of the invention relates to the use of the composite sheet material above, so as to be able to profit from the advantages of the composite sheet material.

Finally, the invention provides for a method of producing a roofing underlayment material by coating a film onto a substrate comprising arranging that the substrate forms at least a part of a first surface at the exterior of the composite sheet material. The method further comprises arranging that the part of the first surface has a coefficient of friction with a minimum value of 0.50, 0.70, 0.73 or 0.80 as measured in accordance with ASTM F-1679 under dry conditions.

This aspect of the invention relates to the production of the composite sheet material according to an earlier aspect of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 is a schematic cross sectional view of the composite sheet material of the present invention;

FIG. 2 is a schematic diagram showing equipment suitable for producing the composite sheet material of the present invention; and

FIG. 3 is a view of a roofing system that includes the composite sheet material of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

The present invention is directed to a roofing underlayment material for use in roofing systems that comprises a composite sheet material that is flexible, relatively lightweight, resistant to water as well as being water vapor permeable and resistant to tearing. The inventors has realized that a synthetic roofing underlayment can give water barrier properties, breathability, good tensile and tear strength, excellent resistance to UV light, resistance to algae, fungi and mold, resistance to rot and decay, etc. The underlayment material helps to protect the interior of the building including the insulating materials underneath against moisture, dust, blowing snow, wind, and the like. In particular, the underlayment material provides a breathable membrane that permits moisture vapor to escape through the roofing system while being a barrier to water so that penetration of water into the building is prevented.

In addition to the aforementioned desirable properties, underlayment materials in accordance with embodiments of the present invention can also help provide a roofing structure, such as a shingled roof, with fire resistance so that the roof can meet the Fire Resistance requirements of ASTM E 108-07a, Class A. Under ASTM E 108-07a, the fire resistance characteristics of a roofing covering are evaluated under a simulated fire originating outside the building. Class A tests are applicable to roof coverings that are effective against severe test exposure, afford a severe degree of fire protection to the roof deck, do not slip from position, and do not present a flying brand hazard. To meet the requirements of Test A, a roofing system incorporating the composite sheet material as an underlayment must past a Burning Brand test, Spread of Flame Test, and an Intermittent Flame test.

In an embodiment (illustrated in FIG. 1) an underlayment material based on a composite sheet material (10) includes a (nonwoven or woven) fibrous substrate (12) and a film layer (14) extending uninterruptedly and continuously over one surface of the nonwoven fibrous substrate (22). Examples of woven substrates include woven fabrics as well as woven slit films. The film layer can be attached to the substrate layer in a variety of ways including extrusion, lamination, roller application, doctor blades, spray coatings, and the like. In a preferred embodiment, the film is extruded directly onto the surface of the substrate.

In the embodiment, the film layer is extrusion coated directly onto a surface of the substrate so that the film layer (14) has a strong adherence to the substrate (12). As a result, the film layer and the substrate are not subject to delamination but instead are structurally combined with one another to form a composite material. The peel adhesion of the film layer (14) to the substrate (12) is at least 59 g/cm (150 grams/inch). High peel adhesions are preferred as when the substrate and film layer delaminate, it is more difficult to walk on the composite sheet material which may be dangerous when the composite sheet material is placed on a roof. In an embodiment the peel adhesion is 78 g/cm (200 grams/inch). Most desirably, the adhesion is so great that the fibers of the substrate will tear or break before delamination will occur. This condition, known as “fiber tear,” occurs above about 98 g/cm (250 grams/inch). Adhesion of the film to the substrate is measured in accordance with the test procedure described below under the section entitled “Test Methods.”

Generally speaking, the breathability of the composite sheet material may be controlled as desired for the intended application of the materials. In barrier applications, it is generally desirable that the composite sheet material has a moisture vapor transmission rate (MVTR) that is at least 35 g/m²/day at 50% relative humidity and 23° C. (73° F.) (e.g., perm of 5 or greater), and more desirably an MVTR of at least 50. In one embodiment, the composite sheet material has a MVTR that is at least 100 g/m²/day. In some embodiments, the composite sheet material may have a MVTR of greater than about 150 g/m²/day, more specifically greater than about 300 g/m²/day, and even more specifically greater than about 500 g/m²/day. Typically, underlayment applications do not require high moisture vapor transmission rates and will often have a moisture vapor transmission rate of less than about 2000 g/m²/day. It should be understood however that materials having higher moisture vapor transmission rates are equally within the scope of the invention. In barrier applications it may also be desirable for the composite sheet material to be impermeable to air flow. Preferably, the composite sheet material has an Air Leakage Rate less than 0.02 L/(s·m²), and more desirably less than 0.015 L/(s·m²). Moisture vapor transmission and Air Leakage rates are measured in accordance with the test procedures described below under the section entitled “Test Methods.”

The substrate functions to support and carry the film layer as well as to provide strength to the overall composite sheet material. In a preferred embodiment the substrate is a nonwoven substrate comprised of a plurality of polymeric fibers or filaments that are randomly dispersed and bonded to one another at points of intersection to form a nonwoven web having excellent strength. Suitable polymeric materials for the nonwoven substrate may include polyolefins, polyamides, polyesters, polyacrylates, or other fiber-forming polymers. In a preferred embodiment, the nonwoven substrate comprises randomly-laid spunbonded fibers, for example a spunbonded polyolefin such as polyethylene, polypropylene, or combinations thereof. Suitable spunbonded nonwovens may have a basis weight equal to or greater than about 0.3 oz/yd². As discussed in greater detail below, a particularly preferred nonwoven substrate comprises a spunbonded polypropylene having a basis weight equal to or greater than about 1 oz/yd², and more specifically, a spunbonded polypropylene having a basis weight of equal to or greater than about 1.5 oz/yd². Spunbonded nonwoven fabrics suitable for use in the composite sheet material have fiber deniers in the range of 4 to 20.5, more specifically from about 7 to about 12, with spunbonded fabrics having fiber deniers at the higher end of this range being preferred. The denier for example is 4.0, 7.7, 10 or 20.

Preferably, the substrate 12 is a high tenacity nonwoven fabric formed from polymeric fibers which are randomly disposed and bonded to one another to form a strong nonwoven web. It is important for the substrate to have high tenacity and relatively low elongation in order to provide the strength and other physical properties required for a barrier material such as a roof underlayment. Preferably, the substrate 12 has a grab tensile strength of at least 133 Newtons (30 pounds), and more preferably at least 178 Newtons (40 pounds) in at least one of the machine direction (MD) or the cross-machine direction (CD). More preferably, the substrate has a grab tensile strength of at least 267 N (60 pounds) in at least one of the MD and the CD. In one embodiment, the substrate 12 has a grab tensile strength of at least 165 Newtons (37 pounds) in the CD.

In addition to the high strength properties mentioned above, it is desirable for the surface of the substrate to have non-skid properties. Preferably, the surface of the substrate has a coefficient of friction that is from about 0.50 to 1.0 and more desirably from at least 0.70, and most desirably at least 0.80 as measured in accordance with ASTM F-1679. In one embodiment, the coefficient of friction for the surface of the substrate ranges from 0.70 to about 0.90, and in particular, from about 0.73 to 0.88. Advantageously, the non-skid surface of the composite sheet material can be provided in the absence of using additional coatings or gritty materials as is common in other underlayment materials.

In some embodiments, it may also be desirable for the substrate to have a Martindale Abrasion this is between 0.2 and 0.4, and in particular, from about 0.2 to 0.35, and more particularly, from about 0.25 to 0.3. The Martindale Abrasion rating of the substrate is indicative of how much fiber, as a percentage, is rubbed or abraded off of the fabric after a set number of cycles. If the number is low (e.g., less than 0.4), the fibers tend to be more locked down into the substrate and generally resist rolling or pilling up. In the present invention, it is believed that the relatively low Martindale Abrasion rating and the high coefficient of friction, provides a composite sheet material in which the fibers of the substrate are adhered tighter to the surface of the substrate so as to provide a better traction surface, and because the fibers resisting rolling or pilling, the surface retains its integrity and non-skid properties, even after repeatedly being walked on. Martindale Abrasion is determined in accordance with INDA standard WSP-20.5 (40 cycles).

As shown in FIG. 1, the substrate 12 includes surface 18 that defines an outer surface of the composite sheet material, and hence, an outer surface of the underlayment material. Surface 18 provides a substantially non-skid surface such that the composite sheet material is particularly useful in roofing applications where slippage by workers installing shingles or other roofing materials can be a concern. In particular, the composite sheet material of the present invention can be utilized as an underlayment material in which the sheet material is positioned so that the film layer faces towards the roof structure (i.e., roof deck) and the substrate faces outwardly to provide a non-skid surface. In this way, workers installing a roof are able to work on the surface of the composite sheet material while the possibility of slipping is minimized in contrast to some other forms of underlayment materials. Additionally, the high strength properties of the substrate helps prevent tearing or ripping of the sheet material during roof installation.

One specific example of a commercially available nonwoven fabric possessing the required high levels of strength is a product sold under the trademark TYPAR® or TELKTON® by Fiberweb, Inc. This product is a spunbonded nonwoven fabric made from fibers in the form of substantially continuous filaments of polypropylene. The filaments are mechanically cold-drawn and have a denier per filament of from 4 to 20. They preferably exhibit a fiber birefringence of at least 0.022. The fabric is area bonded, with the filaments being bonded to one another at their crossover points to form a nonwoven sheet material having excellent strength characteristics. The spunbonded nonwoven substrate preferably has a grab tensile strength in the machine direction (MD) of at least 267 N (60 lbs.) and in the cross machine direction (CD) of at least 178 N (40 lbs.). The nonwoven substrate is manufactured generally in accordance with Kinney U.S. Pat. No. 3,338,992, using mechanical draw rolls as indicated in FIG. 16. An example of another suitable spunbonded nonwoven fabric is a product sold by Fiberweb, Inc. under the trademark REEMAY®. This spunbonded nonwoven fabric is formed of filaments of polyester.

Other examples of nonwoven substrates that may be used in some embodiments of the invention include flash spun nonwoven materials such as a flash spun high density polyethylene nonwoven material commercially available from DuPont de Nemours Co. under the trade name TYVEK®. The flash spun nonwoven materials are available in a range of basis weights and are suitable for use in the breathable materials of the invention. In certain embodiments, the flash spun nonwoven materials will have a basis weight in a range of from about 0.7 to about 4 oz/yd².

In one embodiment, the required high tenacity and low elongation of the nonwoven substrate are achieved by selection of a manufacturing process in which the polymer fibers of the nonwoven fabric are drawn to achieve a high degree of molecular orientation, which increases fiber tenacity and lowers fiber elongation. Preferably, the manufacturing process involves mechanically drawing the fibers by means of draw rolls, as distinguished from other well-known manufacturing processes for nonwovens which utilize pneumatic jets or slot-draw attenuators for attenuating the freshly extruded fibers. Pneumatic attenuation of the fibers via jets or attenuators can not achieve the high spinline stress required for orienting the polymer molecules to a high degree to develop the full tensile strength capability of the fibers. Mechanically drawing the fibers, on the other hand, allows for higher stresses in the fiber to orient the polymer molecules in the fibers and thereby strengthen the fibers. The drawing is carried out below the melting temperature of the polymer, after the polymer has cooled and solidified. This type of drawing process is conventionally referred to as “cold-drawing” and the thus-produced fibers may be referred to as “cold-drawn” fibers. Because the fibers are drawn at a temperature well below the temperature at which the polymer solidifies, the mobility of the oriented polymer molecules is reduced so that the oriented polymer molecules of the fiber cannot relax, but instead retain a high degree of molecular orientation. The degree of molecular orientation of the fiber can be determined by measuring the birefringence of the fiber. Cold-drawn fibers of the type used in the present invention are characterized by having a higher birefringence than fibers attenuated by pneumatic jets or slot-draw attenuators. Consequently, the individual fiber tenacity of a cold-drawn fiber is significantly greater than that of a fiber which is attenuated or stretched by pneumatic jets or attenuators of the type used in some spunbond nonwoven manufacturing processes.

Cold-drawing of a fiber-forming polymer is characterized by a phenomenon known as “necking down”. When the undrawn fiber is stretched, a reduction in diameter occurs in the fiber at a discrete location, i.e. “neck” instead of a gradual reduction in diameter. The morphology of a fiber drawn by cold-drawing is different from the morphology of a fiber which has been attenuated or stretched while still in the molten state where the polymer molecules are mobile. The differences are evident from the x-ray diffraction patterns, from birefringence measurements, and from other analytical measurements.

Also contributing to the required high strength and low elongation of the substrate is the method or mechanism by which the fibers are bonded. Preferably, the nonwoven substrate is “area bonded” as distinguished from a “point bonded” or “patterned bonded” sheet material. In a point bonded or pattern bonded fabric, discrete bond points or zones are separated from one another by unbonded areas or zones. This type of bonding is often utilized for applications in which it is desired to preserve the softness of the fabric, such as nonwoven fabrics for diapers or hygiene products for example. In an “area bonded” fabric, the fiber bonds are not separated by unbonded areas, but instead are found throughout the area of the fabric. Because of the larger number of fiber-to-fiber bonds, area bonded fabrics are typically stronger than a point bonded fabric and are also less soft and less flexible. The fibers are adhered or bonded to one another throughout the fabric at numerous locations where the randomly deposited fibers overlie or cross one another.

The thermoplastic polymer fibers or filaments of the nonwoven substrate 12 preferably contain pigments as well as chemical stabilizers or additives for retarding oxidation and ultraviolet degradation, and for imparting other desired properties such as antimicrobial, antimold, or antifungal. Typically, the stabilizers and additives are incorporated in the polymer at conventional levels, e.g., on the order of about 0.5 to 2% by weight. Typical stabilizers may include primary antioxidants (including hindered amine-light stabilizers and phenolic stabilizers), secondary antioxidants (such as phosphates), and ultraviolet absorbers (such as benzophenones). The polymer composition also preferably contains a pigment to render the nonwoven fabric opaque. In one preferred embodiment, the fibers are pigmented black using a black pigment, such as carbon black. If a white color is desired, titanium dioxide pigment can be used at comparable levels, or blends of titanium dioxide, with carbon black or with other colored pigments could be employed. The fibers or filaments are preferably circular in cross-section, although other cross-sectional configurations such as trilobal or multilobal cross-sections can be employed if desired.

The substrate 12 typically has a basis weight of at least 50 g/m², preferably from 60 to 140 g/m², and for certain preferred embodiments, a basis weight of from 80 to 110 g/m².

The film layer 14 comprises a polymeric material having water barrier properties and that is inherently or that can be rendered breathable to moisture vapor. The influence of the substrate on the moisture vapor transmission rate is negligible compared to that of the film. In an embodiment the film layer, and hence the composite sheet material has a moisture vapor transmission rate with a value of at least 35. In further embodiments, the value is from about 50 to 110 g/m²/24 hr. 50% relative humidity and 23° C. The film layer also has a hydrostatic pressure of at least 55 cm, or at least 100 cm. In further embodiments the film layer has a hydrostatic pressure from about 500 to 900 cm.

In one embodiment, the film layer comprises a polymeric composition that is rendered microporous so that a desired moisture vapor transmission rate can be achieved. As discussed in greater detail below, the composition from which the film layer 14 is formed may be prepared by blending or compounding one or more thermoplastic polymers with suitable inorganic pore-forming fillers and with suitable additives, stabilizers and antioxidants.

Suitable polymers for the polymer composition of the coating include any thermoplastic polymers or blends of such polymers which may be extruded directly onto the nonwoven substrate as a film such that the film and the nonwoven substrate are structurally combined with each other. Such polymers include, but are not limited to, polyolefins, polyesters, polyamides, thermoplastic polyurethanes, polyvinyl chloride, polystyrene, and copolymers of these polymers. In a preferred embodiment, the polymer composition includes at least one polyolefin polymer component, such as polypropylene, propylene copolymers, homopolymers or copolymers of ethylene, or blends of these polyolefins. The polymer composition may, for example, comprise 100% polypropylene homopolymer, or blends of polypropylene and polyethylene. Suitable polyethylenes include linear low density polyethylene (LLDPE). The polymer composition may also include minor proportions of other nonolefin polymers.

Suitable fillers for use in the respective film coatings include, but are not limited to, various organic and/or inorganic materials. In a specific embodiment, the filler may comprise one or more finely powdered inorganic materials such as metal oxides, metal hydroxides, metal carbonates and the like. Preferred fillers include, but are not limited to, calcium carbonate, clay, silica, kaolin, titanium dioxide, diatomaceous earth, or combinations of these materials. Calcium carbonate is particularly preferred as a pore-forming filler.

The particle size of the filler may be selected in order to influence the micropore size in the coating and consequently the breathability of the material product. Preferably, the pore-forming filler has a particle size of no more than about 5 microns, and in particular, the filler typically has an average particle size of from about 0.5 to about 5 microns. The filler may optionally include a surface coating to facilitate dispersion of the filler in the polymer composition, to increase the ability of the filler to repel water, and/or to increase incompatibility of the filler with the polymer composition and the formation of micropores at the vicinity of the filler. Suitable surface coatings include but are not limited to organic acids such as stearic or behenic acid, salts of organic acids such as calcium stearate, fatty acids and salts thereof, nonionic surfactants, and similar such coatings. For example, in a preferred embodiment the filler comprises calcium carbonate that has been treated with calcium stearate to render it hydrophobic and to prevent agglomeration or clumping.

Generally, the filler is included in the film layer in an amount suitable to provide the desired breathability. Generally, the filler may be employed in an amount of from about 25 to about 75 weight percent, based on the total weight of the microporous coating. To achieve the desired level of MVTR for the present invention, it is preferred that the polymer and pore-forming filler blend comprise at least 40% by weight filler, and most desirably at least 50% by weight filler. The polymer composition may also include additional colorants or pigments, such as titanium dioxide, as well as conventional stabilizers and antioxidants, such as UV stabilizers, thermal stabilizers, hindered amine light stabilizer compounds, ultraviolet absorbers, antioxidants and antimicrobials.

In one embodiment of the invention, the composite sheet material 10 is manufactured by extrusion coating the substrate 12 with a composition comprising a polymer composition and a filler to form film layer 14 on the substrate, followed by manipulating the composite sheet material 10 to render the film layer microporous, and hence breathable. Suitable equipment for carrying out this process is shown schematically in FIG. 2. The substrate 12 is unwound from a supply roll 20 and is directed onto and around a rotating chill roll 22. A cooperating pressure roll 24 defines a pressure nip with the chill roll 22. The polymer composition is extruded in the form of a film 14 of molten polymer from a slot die 26 of an extruder 27 directly into the nip defined between the cooperating rolls 22, 24. As the polymer film 14 and the substrate 12 advance around the chill roll 22, the molten polymer composition cools and solidifies to form a substantially continuous polymer film layer adhered to one surface of the substrate 12. At this point, the nonwoven web and film composite is substantially impermeable to moisture vapor. The composite is made microporous by stretching the material in the machine direction, or the cross-machine direction or in both the machine direction and the cross-machine direction. The fabric can be rolled-up and the stretching can be carried out in a separate subsequent operation, or alternatively, the stretching can be carried out in-line with the extrusion coating operation, as shown in FIG. 2. An exemplary process that may be used to prepare a composite sheet material in accordance with the present invention are described in commonly assigned U.S. Patent Publication No. 2004/0029469, the contents of which are incorporated by reference.

As noted above, the polymer composition, in combination with the filler, can be rendered microporous by a relatively small degree of moving, twisting, calendering, or otherwise physically treating the composite sheet material. In some embodiments, the mere presence of the filler in the film layer is sufficient to render the film layer microporous. In particular, it has been surprisingly discovered that even a small amount of tension applied to the composite sheet material 10 may be enough to render the sheet material breathable. Other methods of rending the film layer microporous may include physical manipulation of the composite sheet material 10, such as bending, twisting, or biasing, can be used to enhance the breathability of the coated substrate.

Various stretching techniques can also be employed to develop the micropores in the composite sheet material 10. A particularly preferred stretching method is a process known as “incremental stretching”. In an incremental stretching operation, the sheet material is passed through one or more cooperating pairs of intermeshing grooved or corrugated rolls which cause the sheet material to be stretched along incremental zones or lines extending across the sheet material. The stretched zones are separated by zones of substantially unstretched or less stretched material. The incremental stretching can be carried out in the cross machine direction (CD) or the machine direction (MD) or both, depending upon the design and arrangement of the grooved rolls. Example of apparatus and methods for carrying out incremental stretching are described in U.S. Pat. Nos. 4,116,892; 4,153,751; 4,153,664; and 4,285,100, incorporated herein by reference.

FIG. 2 illustrates equipment suitable for a continuous in-line stretching operation using first and second pairs of intermeshing rolls. The first, pair of intermeshing rolls 31, 32 is provided with a grooved surface configured for achieving incremental stretching in the cross-direction (CD) of the material. The grooves extend circumferentially around the rolls and produce a series of alternating stretched and non-stretched zones extending linearly along the machine direction of the composite material. The amount of incremental stretching is controlled by varying the engagement depth of the intermeshing rolls. The stretching operation is carried generally in accordance with the teachings of U.S. Pat. No. 5,865,926, the disclosure of which is incorporated herein by reference.

Preferably, the fabric is subjected to stretching in the machine direction as well as in the cross-direction. For this purpose, the fabric is run through a second set of rolls 33, 34 designed for achieving MD stretching. The second pair of intermeshing rolls 33, 34 have a grooved surface configured for achieving stretching in the machine direction (MD) of the material, with the grooves extending generally parallel to the rotational axis of the rolls. The additional stretching operation in the machine direction increases the moisture vapor transmission properties of the material and provides an aesthetically pleasing surface appearance.

It has been discovered that the fire resistance of the composite sheet material, and hence a roofing system including the composite sheet material of the present invention, can be significantly improved by applying the film layer at a relatively high basis weight. In particular, it has been discovered that the composite sheet material employing the above described film layer that is applied at a basis weight of at least 70 g/m² can help provide a roofing structure, such as a shingled roof, with fire resistance so that the roof can meet the Fire Resistance requirements of ASTM E 108-07a, Class A. As noted previously, Class A tests are applicable to roof coverings that are effective against severe test exposure, afford a severe degree of fire protection to the roof deck, do not slip from position, and do not present a flying brand hazard. In one embodiment, the film layer is preferably applied to the nonwoven substrate at a minimum basis weight of 70 g/m², and most desirably, from about 70 to 100 g/m², and even more desirably, from about 75 to 85 g/m². In some embodiments, the film can be applied at a basis of less than 70 g/m², such as at 50 g/m² or greater, although not necessarily with equivalent results. The resulting composite sheet material has an overall basis weight of from about 90 to 205 g/m², and more desirably from about 140 to 205 g/m² and a MVTR of at least 35 g/m²/24 hr. at 50% relative humidity and 23° C. (73° F.), and more desirably and MVTR of at least 100. In one embodiment, the composite sheet material has an MVTR of from about 1 to 411, and desirably from about 7 to 205, and most desirably from about 34 to 137 g/m²/24 hr. at 50% relative humidity and 23° C. (73° F.). The product preferably also has a Gurley porosity of at least 400 seconds and a hydrostatic head of at least 55 cm.

Composite sheet materials in accordance with the present invention, desirably exhibit excellent strength and tear resistant properties so that the sheet materials are particularly useful as a roof underlayment material where the underlayment may be subject to frequent foot traffic as well as other conditions that could damage conventional underlayment materials. In one embodiment, the composite sheet material a grab tensile strength from about 100-150 Newtons, and preferably from about 125 to 140 Newtons, and more preferably, from about 130-140 Newtons in the machine direction (CD). Embodiments of the composite sheet material may also have grab tensile strength in the cross direction from about 80 to 140 Newtons, and preferably from about 100 to 140 Newtons, and more preferably, from about 130 to 140 Newtons. In addition to excellent tensile strength properties, it is also desirable for the composite sheet material to be tear resistant. For example, the composite sheet material desirably has a Trapezoidal Tear Strength in at least one of the machine or cross directions that is from about 30 to 45 Newtons, and desirably from about 34-42 Newtons, and more desirably from about 35 to 40 Newtons. Grab Tensile Strength is measured in accordance with ASTM D 1682, and trapezoidal tear strength is measured in accordance with ASTM D 4533.

In an alternative embodiment, a composite sheet material in accordance with the present invention can be prepared in which the film layer is inherently breathable and therefore does not require the presence of micropores or pore-forming fillers to provide the desired breathability. In particular, in one embodiment the composite sheet material comprises a nonwoven substrate onto which a breathable monolithic film is extrusion coated. In a preferred embodiment, the film forming polymer composition comprises a blend of polypropylene and from about 20 to 30% by weight of a co-polyether amide, a block co-polyether ester, or a combination thereof. Additionally, the polymer composition will include one or more compatibilizers. Examples of compatibilizers include waxes, such as Epolene E-43 and fluoropolymer processing aids (PPA).

Preferably, the monolithic film has a MVTR of at least 35 g/m²/24 hr. at 50% relative humidity and 23° C. (73° F.), and more desirably and MVTR of at least 100. The product preferably also has a Gurley porosity of at least 400 seconds and a hydrostatic head of at least 55 cm. The substrate is as described above with a spunbond polypropylene nonwoven fabric being preferred.

From the foregoing discussion, it can be seen that the present invention provides a composite sheet material that is particularly useful as an underlayment in roofing applications. In this regard, FIG. 3 illustrates a building having a roofing system that is in accordance with the present invention is illustrated and is indicated generally by reference character 50. A portion of the roofing system is not shown so that the reader can see various components of the roofing system. The roofing system 52 includes an exterior roof surface 54, also referred to as a roof deck, a layer of underlayment material 56 attached to the roof deck, and a multiplicity of courses of roofing shingles 58 attached and overlying the underlayment material.

The underlayment material 56 comprises composite sheet material 10. Preferably, the composite sheet material is positioned on the roof deck so that the surface 18 of the substrate faces upwardly and the film layer of the composite sheet material faces towards the roof deck. As noted above, surface 18 provides a non-skid surface that can help prevent slippage of workers installing the roofing system. Additionally, the high strength properties of the nonwoven substrate help to prevent the composite sheet material from being torn or damaged during the installation process.

Test Methods

In the description above and in the non-limiting examples that follow, the following test methods were employed to determine various reported characteristics and properties. ASTM refers to the American Society for Testing and Materials, AATCC refers to the American Association of Textile Chemists and Colorists, INDA refers to the Association of the Nonwovens Fabrics Industry, and TAPPI refers to the Technical Association of Pulp and Paper Industry.

The following tests are hereby incorporated by reference.

Basis Weight is a measure of the mass per unit area of a sheet and was determined by ASTM D-3776, which is hereby incorporated by reference, and is reported in g/m². Fabric thickness is measured in accordance with ASTM D 1777—Standard Test Method for Thickness of Textile Materials (1996).

Air Leakage Rate is a measure of determining air leakage across a specimen under specified differential pressure conditions across the specimen. This test is carried out in accordance with ASTM E 283 and E 2178.

Grab Tensile Strength is a measure of breaking strength of a fabric when subjected to unidirectional stress. This test is carried out in accordance with ASTM D 1682.

Gurley Porosity is a measure of the resistance of the sheet material to air permeability, and thus provides an indication of its effectiveness as an air barrier. It is measured in accordance with TAPPI T-460 (Gurley method). This test measures the time required for 100 cubic centimeters of air to be pushed through a one-inch diameter sample under a pressure of approximately 4.9 inches of water. The result is expressed in seconds and is frequently referred to as Gurley Seconds.

Hydrostatic Head (hydrohead) is a measure of the resistance of a sheet to penetration by liquid water under a static pressure. The test is conducted according to AATCC-127, which is hereby incorporated by reference, and is reported in centimeters.

Moisture Vapor Transmission Rate (MVTR) is determined by ASTM E 96, Standard Test Methods for Water Vapor Transmission of Materials; 1995, Procedure A. Peel Strength is measured in accordance with ASTM D 2724.

Tear Strength is measured in accordance with ASTM D 4533 (trapezoidal tear), tensile strength measurements are determined according to ASTM D 5034-95.

Slip Resistance is measured in accordance with ASTM F-1679.

External Fire Resistance of Roof Covering Systems is measured in accordance with ASTM E 108-07a, Standard Test Methods for Fire Tests of Roof Coverings: Class A Burning Brand and Intermittent Flame.

EXAMPLES

TYPAR® 3251 material, a spunbonded polypropylene nonwoven fabric produced by Fiberweb, Inc. of Old Hickory, Tenn., was used as the fibrous nonwoven substrate for producing a high MVTR extrusion coated composite sheet material. TYPAR® 3251 material is a spunbond polypropylene nonwoven fabric having a basis weight of 84 g/m², a thickness of 0.422 mm (12.7 mils), an MD grab tensile strength of 467 N (105 lbs.), a CD grab tensile strength of 472 N (106 lbs.), and a trapezoidal tear strength of 182 N (41 lbs.) in the MD and 165 N (37 lbs.) in the CD. This substrate was extrusion-coated with a polyolefin polymer composition that is a blend of polypropylene and polyethylene and that contains about 50 percent by weight calcium carbonate filler. The polymer film was extruded onto the substrate at a basis weight of 80 g/m². The resulting composite was incrementally stretched in the MD and CD using equipment similar to that shown in FIG. 2. The physical properties of samples of the composite sheet material were evaluated. Average values for the samples are shown in Table 1 below.

TABLE 1 Test Result Film Basis Weight (g/m2)    80 Peel Adhesion (g/1 inch) >500 Hydrohead (cm) >100 MVTR (g/24 hr m²)    72 Gurley Porosity >400 Thickness, mm (mils)    19 Grab Tensile, MD N (lbf/in)   178 (40) Grab Tensile, CD N (lbf/in   165 (37)

In the following Example, the non-skid properties of the composite sheet material were compared to those of 4 commercially available underlayment materials. The three synthetic underlayments: Titanium UDL, Palasade and REX Synfelt, are all woven slit film (e.g., polypropylene) substrates extrusion coated on one or both side with a polymeric coating, such as polypropylene or a blend. The Titanium product has the coating textured on one side to improved slip performance, while the Palisades has been laminated to a pointbonded nonwoven with printed raised dots to also improve slip performance. The REX Synfelt underlayment has not been specifically altered to improve coefficient of friction. The final sample is 15 pound felt paper, which is commonly a kraft paper impregnated with petroleum byproducts. The results are summarized in TABLE 2 below.

TABLE 2 Average Average Wet Surface Tested Dry (COF) (Slip-Resistance Index) Inventive Composite   0.88 0.73 Sheet Material Titanium ™ UDL   0.87* 0.60* Palasade ™   0.89 0.52 REX ™ Synfelt >1.00 0.47 GAF ShingleMate #15 >1.00 0.69 *Directional slip-resistance was evident with this product.

The fire resistance of the composite sheet material was also tested in accordance with ASTM E 108-07a. The sheet material passed the Class A Burning Brand Test and Class A Intermittent Flame Test.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 

1. A method of installing a roof system on a building comprising covering an exterior surface of a roof structure with a breathable, composite sheet material having water barrier and fire resistant properties, the composite sheet material including a woven or nonwoven substrate defining an upper surface of the sheet material, and an extrusion coated film layer covering an opposite surface of the nonwoven substrate and defining a lower surface of the sheet material, wherein the film layer has a moisture vapor transmission rate of at least 35 g/m²/24 hr. at 50% relative humidity and 23° C., and a hydrostatic heads of at least 55 cm; and positioning the composite sheet material onto the roof structure so that that the film layer faces towards the roof structure and the nonwoven substrate faces outwardly to provide a non-skid surface.
 2. The method of claim 1, wherein the film layer comprises a polyolefin polymer and at least 40% by weight inorganic filler.
 3. The method of claim 1, wherein said film layer comprises at least 40% by weight inorganic filler, and sheet material has been subjected to stretching in both the CD and the MD by incremental stretching to impart to the composite fabric a moisture vapor transmission rate (MVTR) of at least 100 g/m²/24 hr. at 50% relative humidity and 23° C.
 4. The method of claim 1, wherein the film layer has a basis weight that is from about 70 to 100 g/m².
 5. The method of claim 1, wherein the film layer has a basis weight that is at least about 80 g/m².
 6. The method of claim 1, wherein the non-skid surface of the composite sheet material has a coefficient of friction that is at least 0.70.
 7. The method of claim 1, wherein the non-skid surface of the composite sheet material has a coefficient of friction that is from about 0.73 to 0.88.
 8. The method of claim 1, wherein the film layer is a monolithic film comprising a blend of polypropylene and from about 20 to 30% by weight of a co-polyether amide, a block co-polyether ester, or a combination thereof.
 9. The method of claim 1, further comprising the step of attaching a plurality of shingles to the composite sheet material.
 10. The method of claim 9, wherein the roof system comprising the composite sheet material meets the requirements of ASTM E 108 Class A Fire Resistant Test.
 11. The method of claim 1, wherein the nonwoven substrate is a spunbond nonwoven fabric comprising polypropylene continuous filaments.
 12. A composite sheet material useful as a waterproof underlayment for a roof of a structure, the sheet material comprising a woven or nonwoven substrate and a film layer covering a surface of the nonwoven substrate, the film layer comprising a polyolefin polymer and at least 40% by weight inorganic filler, and wherein the composite sheet material has a moisture vapor transmission rate (MVTR) of at least 34 g/m²/24 hr. at 50% relative humidity and 23° C., and a hydrostatic heads of at least 55 cm, and wherein the film layer has a basis weight of at least 80 g/m².
 13. The sheet material of claim 12, wherein the s sheet material has been subjected to stretching in both the CD and the MD.
 14. The sheet material of claim 13, wherein the film layer is extrusion coated onto the substrate and wherein composite sheet material has been incrementally stretched to render the composite sheet material breathable.
 15. The sheet material of claim 12, wherein a roof system comprising a roof deck, a plurality of covering shingles and the composite sheet material as an underlayment material disposed between the roof deck and shingles meets the requirements of ASTM E 108 Class A Fire Resistant Test.
 16. The sheet material of claim 12, wherein the substrate includes an exposed non-skid surface having a coefficient of friction that is from 0.70 to about 0.90.
 17. The sheet material of claim 12, wherein the substrate includes an exposed non-skid surface having a coefficient of friction that is from about 0.73 to 0.88.
 18. The sheet material of claim 12, wherein the film layer includes a UV stabilizer, a thermal stabilizer, or a combination thereof.
 19. A roofing system comprising: a) a roof deck of a building; b) an underlayment material attached to said roof deck, wherein the underlayment material comprises a composite sheet material having water barrier and fire resistant properties, the composite sheet material including a nonwoven substrate defining an upper surface of the sheet material, and an extrusion coated film layer covering an opposite surface of the nonwoven substrate and defining a lower surface of the sheet material that faces towards the roof deck, wherein the film layer has a moisture vapor transmission rate of at least 35 g/m²/24 hr. at 50% relative humidity and 23° C., and a hydrostatic heads of at least 55 cm; and c) a multiplicity of courses of roofing shingles attached to said underlayment material, and wherein the roof system meets the requirements of ASTM E 108 Class A Fire Resistant Test.
 20. The roofing system of claim 19, wherein said film layer comprises at least 40% by weight inorganic filler, and sheet material has been subjected to stretching in both the CD and the MD by incremental stretching to impart to the composite fabric a moisture vapor transmission rate (MVTR) of at least 100 g/m²/24 hr. at 50% relative humidity and 23° C. and a hydrostatic head of at least 55 cm.
 21. The roofing system of claim 19, wherein the film layer has a basis weight that is from about 70 to 100 g/m².
 22. The roofing system of claim 19, wherein the film layer has a basis weight that is at least about 80 g/m².
 23. The roofing system of claim 19, wherein the non-skid surface of the composite sheet material has a coefficient of friction that is at least 0.70.
 24. The roofing system of claim 19, wherein the non-skid surface of the composite sheet material has a coefficient of friction that is from about 0.73 to 0.88.
 25. The roofing system of claim 19, wherein the film layer is a monolithic film comprising a blend of polypropylene and from about 20 to 30% by weight of a co-polyether amide, a block co-polyether ester, or a combination thereof.
 26. A roofing system comprising: a) a roof deck of a building; b) an underlayment material attached to said roof deck, wherein the underlayment material comprises a composite sheet material having water barrier and fire resistant properties, the composite sheet material including a woven or nonwoven substrate and a film layer covering a surface of the substrate, the film having a basis weight of at least 70 g/m² and a moisture vapor transmission rate of at least 35 g/m²/24 hr. at 50% relative humidity and 23° C., and a hydrostatic heads of at least 55 cm; and c) a multiplicity of courses of roofing shingles attached to said underlayment material, and wherein the roof system meets the requirements of ASTM E 108 Class A Fire Resistant Test.
 27. The roofing system of claim 26, wherein the substrate layer faces in the direction of the roof deck.
 28. The roofing system of claim 26, wherein the film layer faces in the direction of the roof deck.
 29. The roofing system of claim 26, wherein the substrate layer comprises a woven slit film. 